1. Field of the Invention
The present invention relates to testing a thin-film magnetic head with a magnetoresistive effect (MR) read head element.
2. Discussion of the Related Art
In order to increase the recording density in hard drive disks, composite thin-film magnetic heads are being produced with an inductive write head element and a magnetoresistive effect (MR) read head element. The basic concept of magnetoresistive element is that resistance of such element changes as a function of applied magnetic field. Such elements can be produced by using an anisotropic magnetoresistive effect (AMR) element, a giant magnetoresistive effect (GMR) element such as a spin-valve MR element or a tunnel magnetoresistive effect (TMR) element to increase element sensitivity.
A magnetic head assembly with a defective MR element cannot perform normal reproduction operation over the range of magnetic read signals from a disk. Accordingly, it is important to qualify each head by testing the head for instabilities or noise.
There are several known techniques for testing MR elements for noise. Unfortunately, conventional testers are inadequate in several applications. For example, conventional systems typically detect large static changes, often referred to as “hard kinks” in the MR elements, which are magnetic instabilities occurring over a small range of magnetic fields, but fail to recognize other instabilities, such as “soft kinks”, which are magnetic instabilities occurring over a large range of magnetic fields. Thus, what is needed is an improved method and apparatus for measuring the performance of magnetic heads that can detect different types of noise, including hard and soft kinks.